U.S. patent number 10,595,722 [Application Number 16/424,246] was granted by the patent office on 2020-03-24 for automatic optical path adjustment in home oct.
This patent grant is currently assigned to Notal Vision Ltd.. The grantee listed for this patent is Notal Vision Ltd.. Invention is credited to Yair Alster, Gidon Goren-Gratzyani, Amit Pascal, Omer Rafaeli.
United States Patent |
10,595,722 |
Pascal , et al. |
March 24, 2020 |
Automatic optical path adjustment in home OCT
Abstract
Retinal imaging systems and related methods employ a user
specific approach for controlling the reference arm length in an
optical coherence tomography (OCT) imaging device. A method
includes restraining a user's head relative to an OCT imaging
device. A reference arm length adjustment module is controlled to
vary a reference arm length to search a user specific range of
reference arm lengths to identify a reference arm length for which
the OCT image detector produces an OCT signal corresponding to the
retina of the user. The user specific range of reference arm
lengths covers a smaller range of reference arm lengths than a
reference arm length adjustment range of the reference arm length
adjustment module.
Inventors: |
Pascal; Amit (Haifa,
IL), Rafaeli; Omer (Udim, IL), Alster;
Yair (Tel Aviv, IL), Goren-Gratzyani; Gidon
(Givatayim, IL) |
Applicant: |
Name |
City |
State |
Country |
Type |
Notal Vision Ltd. |
Tel-Aviv |
N/A |
IL |
|
|
Assignee: |
Notal Vision Ltd. (Tel-Aviv,
IL)
|
Family
ID: |
69902360 |
Appl.
No.: |
16/424,246 |
Filed: |
May 28, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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62740781 |
Oct 3, 2018 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B
5/0066 (20130101); G01B 9/02043 (20130101); A61B
3/102 (20130101); A61B 5/004 (20130101); G01B
9/02091 (20130101); G01B 9/0203 (20130101); G01B
9/02063 (20130101); A61B 3/14 (20130101); G01B
9/02076 (20130101); G01B 2290/35 (20130101) |
Current International
Class: |
A61B
3/10 (20060101); A61B 3/14 (20060101); G01B
9/02 (20060101); A61B 5/00 (20060101) |
Field of
Search: |
;359/206 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
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2019. cited by applicant .
U.S. Appl. No. 16/424,246, "U.S. Application No.", dated May 28,
2019. cited by applicant .
U.S. Appl. No. 16/439,587, "U.S. Application No.", dated Jun. 12,
2019. cited by applicant .
Chakravarthy et al., "Automated Identification of Lesion Activity
in Neovascular Age-Related Macular Degeneration", Opthalmology,
vol. 123, No. 8, Aug. 2016, pp. 1731-1736. cited by applicant .
PCT/IL2018/051172, "International Search Report and Written
Opinion", dated Feb. 27, 2019, 12 pages. cited by applicant .
PCT/IL2018/051174, "International Search Report and Written
Opinion", dated Feb. 26, 2019, 8 pages. cited by applicant .
U.S. Appl. No. 16/404,311, "First Action Interview Pilot Program
Pre-Interview Communication", dated Aug. 15, 2019, 4 pages. cited
by applicant .
U.S. Appl. No. 16/425,362, "First Action Interview Pilot Program
Pre-Interview Communication", dated Aug. 27, 2019, 4 pages. cited
by applicant .
U.S. Appl. No. 16/425,362, "Non-Final Office Action", dated Aug.
23, 2019, 13 pages. cited by applicant .
U.S. Appl. No. 16/439,587, "First Action Interview Pilot Program
Pre-Interview Communication", dated Aug. 30, 2019, 5 pages. cited
by applicant .
U.S. Appl. No. 16/439,587, "Non-Final Office Action", dated Aug.
12, 2019, 14 pages. cited by applicant.
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Primary Examiner: Alexander; William R
Attorney, Agent or Firm: Kilpatrick Townsend & Stockton
LLP
Parent Case Text
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application
No. 62/740,781, filed Oct. 3, 2018, the entire contents of which is
hereby incorporated by reference in its entirety.
Claims
What is claimed is:
1. An ophthalmic imaging system for imaging a retina of a user, the
ophthalmic imaging system comprising: an optical coherence
tomography (OCT) imaging device including a sample arm optical
path, an OCT image detector, a reference arm optical path having a
reference arm length, and a reference arm length adjustment module
controllable to vary the reference arm length over a reference arm
length adjustment range; a housing to which the OCT imaging device
is attached; a viewer assembly coupled with the housing, the viewer
assembly being configured to engage a user's head to restrain the
user's head relative to the housing so that the sample arm optical
path extends to the retina of the user; and a control unit
operatively connected to the OCT image detector and the reference
arm length adjustment module, the control unit being configured to:
control the reference arm length adjustment module during an
initial imaging of the retina of the user to vary the reference arm
length within the reference arm length adjustment range to identify
an initial imaging reference arm length for which the OCT image
detector produces an OCT signal corresponding to the retina of the
user; determine a user specific range of reference arm lengths,
based on the initial imaging reference arm length, that covers a
smaller range of reference arm lengths than the reference arm
length adjustment range; and control the reference arm length
adjustment module during an imaging of the retina of the user
subsequent to the initial imaging of the retina of the user to vary
the reference arm length to search within the user specific range
of reference arm lengths to identify a subsequent imaging reference
arm length for which the OCT image detector produces an OCT signal
corresponding to the retina of the user.
2. The ophthalmic imaging system of claim 1, wherein the user
specific range of reference arm lengths is predetermined.
3. The ophthalmic imaging system of claim 2, wherein the user
specific range of reference arm lengths is based on spatial
information about one or more facial features of the user.
4. The ophthalmic imaging system of claim 3, wherein the one or
more facial features of the user comprise one or more of a forehead
of the user, one or more cheeks of the user, a cornea of an eye of
the user including the retina of the user, and a lateral orbital
rim of the user.
5. The ophthalmic imaging system of claim 3, wherein the spatial
information about one or more facial features of the user is
generated via one or more of: three-dimensional scanning of the one
or more facial features of the user; caliper measurement of the one
or more facial features of the user relative to an eye of the user
that includes the retina of the user; a cast mask of the one or
more facial features of the user; an axial length of the eye of the
user that includes the retina of the user; ultrasound measurement
of the axial length of the eye of the user that includes the retina
of the user; and OCT measurement of the axial length of the eye of
the user that includes the retina of the user.
6. The ophthalmic imaging system of claim 1, comprising an
objective lens assembly, wherein the ophthalmic imaging system does
not include an adjustment mechanism configured to adjust a distance
between the retina of the user and the objective lens assembly.
7. The ophthalmic imaging system of claim 6, wherein the ophthalmic
imaging system is configured to image a field of view on the retina
of the user equal to or less than 15 degrees for the reference arm
length equal to any length within the reference arm length
adjustment range.
8. The ophthalmic imaging system of claim 1, wherein the OCT
imaging device has an image depth of no more than 3 mm.
9. The ophthalmic imaging system of claim 1, wherein the user
specific range of reference arm lengths is less than one-quarter of
the reference arm length adjustment range.
10. The ophthalmic imaging system of claim 1, wherein the control
unit is configured to: receive input of the user specific range of
reference arm lengths; and store the user specific range of
reference arm lengths in a tangible memory device.
11. The ophthalmic imaging system of claim 1, wherein: the control
unit is configured to determine the user specific range of
reference arm lengths by controlling the reference arm length
adjustment module during an imaging of the retina of the user to
vary the reference arm length to search within the reference arm
length adjustment range to identify a user specific imaging
reference arm length for which the OCT image detector produces an
OCT signal corresponding to the retina of the user; and the control
unit determines the user specific range of reference arm lengths
based on the user specific imaging reference arm length.
12. The ophthalmic imaging system of claim 1, wherein the reference
arm length adjustment range encompasses at least a 20 mm range of
reference arm lengths.
13. The ophthalmic imaging system of claim 1, wherein the user
specific range of reference arm lengths encompasses less than a 10
mm range of reference arm lengths.
14. The ophthalmic imaging system of claim 1, further comprising a
sensor that generates a signal indicative of a position of a
feature of the user's head relative to the housing, and wherein the
control unit determines the user specific range of reference arm
lengths based on the signal indicative of the position of the
feature of the user's head relative to the housing.
15. The ophthalmic imaging system of claim 14, wherein the user
specific range of reference arm lengths is determined by the
control unit to account for a change in the position of the feature
of the user's head relative to the initial imaging of the
retina.
16. The ophthalmic imaging system of claim 1, further comprising a
focusing module that is controlled by the control unit to focus
sample light transmitted over the sample arm optical path onto the
retina of the user, wherein a user specific focus setting of the
focusing module is employed during imaging of the retina of the
user.
17. The ophthalmic imaging system of claim 1, wherein the user
specific range of reference arm lengths is calculated by the
control unit to include a predetermined upper incremental range of
the reference arm length longer than the initial imaging reference
arm length and a predetermined lower incremental range of the
reference arm length shorter than the initial imaging reference arm
length.
18. An ophthalmic imaging system for imaging a retina of a user,
the ophthalmic imaging system comprising: an optical coherence
tomography (OCT) imaging device including a sample arm optical
path, an OCT image detector, a reference arm optical path having a
reference arm length, and a reference arm length adjustment module
controllable to vary the reference arm length over a reference arm
length adjustment range; a housing to which the OCT imaging device
is attached; a viewer assembly coupled with the housing, the viewer
assembly being configured to engage a user's head to restrain the
user's head relative to the housing so that the sample arm optical
path extends to the retina of the user; a control unit operatively
connected to the OCT image detector and the reference arm length
adjustment module, the control unit being configured to: store a
user specific range of reference arm lengths that covers a smaller
range of reference arm lengths than the reference arm length
adjustment range; and control the reference arm length adjustment
module to vary the reference arm length to search within the user
specific range of reference arm lengths to identify a reference arm
length for which the OCT image detector produces an OCT signal
corresponding to the retina of the user; and a sensor that
generates a signal indicative of a position of a feature of the
user's head relative to the housing, wherein the control unit
determines the user specific range of reference arm lengths based
on the signal indicative of the position of the feature of the
user's head relative to the housing, and wherein the viewer
assembly comprises a compliant member having a thickness that can
change up to 10 mm in response to change in pressure applied to the
viewer assembly by the user's head.
19. The ophthalmic imaging system of claim 18, wherein the user
specific range of reference arm lengths is determined by the
control unit to account for a change in the position of the feature
of the user's head relative to a prior imaging of the retina by the
imaging system.
20. The ophthalmic imaging system of claim 18, wherein the user
specific range of reference arm lengths is based on spatial
information about one or more facial features of the user.
21. The ophthalmic imaging system of claim 20, wherein the one or
more facial features of the user comprise one or more of a forehead
of the user, one or more cheeks of the user, a cornea of an eye of
the user including the retina of the user, and a lateral orbital
rim of the user.
22. The ophthalmic imaging system of claim 20, wherein the spatial
information about one or more facial features of the user is
generated via one or more of: three-dimensional scanning of the one
or more facial features of the user; caliper measurement of the one
or more facial features of the user relative to an eye of the user
that includes the retina of the user; a cast mask of the one or
more facial features of the user; an axial length of the eye of the
user that includes the retina of the user; ultrasound measurement
of the axial length of the eye of the user that includes the retina
of the user; and OCT measurement of the axial length of the eye of
the user that includes the retina of the user.
23. An ophthalmic imaging system for imaging a retina of a user,
the ophthalmic imaging system comprising: an optical coherence
tomography (OCT) imaging device including a sample arm optical
path, an OCT image detector, a reference arm optical path having a
reference arm length, and a reference arm length adjustment module
controllable to vary the reference arm length over a reference arm
length adjustment range; a housing to which the OCT imaging device
is attached; a viewer assembly coupled with the housing, the viewer
assembly being configured to engage a user's head to restrain the
user's head relative to the housing so that the sample arm optical
path extends to the retina of the user; a control unit operatively
connected to the OCT image detector and the reference arm length
adjustment module, the control unit being configured to: store a
user specific range of reference arm lengths that covers a smaller
range of reference arm lengths than the reference arm length
adjustment range; and control the reference arm length adjustment
module to vary the reference arm length to search within the user
specific range of reference arm lengths to identify a reference arm
length for which the OCT image detector produces an OCT signal
corresponding to the retina of the user; and a sensor that
generates a signal indicative of a position of a feature of the
user's head relative to the housing, wherein the control unit
determines the user specific range of reference arm lengths based
on the signal indicative of the position of the feature of the
user's head relative to the housing, and wherein the signal is
indicative of a position of a feature of the user's forehead
relative to the housing.
24. The ophthalmic imaging system of claim 23, wherein the user
specific range of reference arm lengths is determined by the
control unit to account for a change in the position of the feature
of the user's head relative to a prior imaging of the retina by the
imaging system.
25. The ophthalmic imaging system of claim 23, wherein the user
specific range of reference arm lengths is based on spatial
information about one or more facial features of the user.
26. The ophthalmic imaging system of claim 25, wherein the one or
more facial features of the user comprise one or more of a forehead
of the user, one or more cheeks of the user, a cornea of an eye of
the user including the retina of the user, and a lateral orbital
rim of the user.
27. The ophthalmic imaging system of claim 25, wherein the spatial
information about one or more facial features of the user is
generated via one or more of: three-dimensional scanning of the one
or more facial features of the user; caliper measurement of the one
or more facial features of the user relative to an eye of the user
that includes the retina of the user; a cast mask of the one or
more facial features of the user; an axial length of the eye of the
user that includes the retina of the user; ultrasound measurement
of the axial length of the eye of the user that includes the retina
of the user; and OCT measurement of the axial length of the eye of
the user that includes the retina of the user.
28. An ophthalmic imaging system for imaging a retina of a user,
the ophthalmic imaging system comprising: an optical coherence
tomography (OCT) imaging device including a sample arm optical
path, an OCT image detector, a reference arm optical path having a
reference arm length, and a reference arm length adjustment module
controllable to vary the reference arm length over a reference arm
length adjustment range; a housing to which the OCT imaging device
is attached; a viewer assembly coupled with the housing, the viewer
assembly being configured to engage a user's head to restrain the
user's head relative to the housing so that the sample arm optical
path extends to the retina of the user; an objective lens assembly,
wherein the ophthalmic imaging system does not include an
adjustment mechanism configured to adjust a distance between the
retina of the user and the objective lens assembly; and a control
unit operatively connected to the OCT image detector and the
reference arm length adjustment module, the control unit being
configured to control the reference arm length adjustment module to
vary the reference arm length to identify a reference arm length
for which the OCT image detector produces an OCT signal
corresponding to the retina of the user, wherein the ophthalmic
imaging system is configured to image a field of view on the retina
of the user equal to or less than 15 degrees for the reference arm
length equal to each of all lengths within the reference arm length
adjustment range.
29. The ophthalmic imaging system of claim 28, wherein a user
specific range of reference arm lengths is calculated by the
control unit based on a reference arm length for which the OCT
image detector produces an OCT signal corresponding to the retina
of the user based on a prior imaging of the retina of the user.
30. The ophthalmic imaging system of claim 28, comprising an
objective lens assembly, wherein the ophthalmic imaging system does
not include an adjustment mechanism configured to adjust a distance
between the retina of the user and the objective lens assembly.
Description
BACKGROUND
Macular degeneration is the leading cause of vision loss in the
United States of America. In macular degeneration, the central
portion of the retina (a.k.a., the macula) deteriorates. When
healthy, the macula collects and sends highly detailed images to
the brain via the optic nerve. In early stages, macular
degeneration typically does not significantly affect vision. If
macular degeneration progresses beyond the early stages, vision
becomes wavy and/or blurred. If macular degeneration continues to
progress to advanced stages, central vision may be lost.
Although macular degeneration is currently considered to be
incurable, treatments do exist that may slow the progression of the
disease so as to prevent severe loss of vision. Treatment options
include injection of an anti-angiogenic drug into the eye, laser
therapy to destroy an actively growing abnormal blood vessel(s),
and photodynamic laser therapy, which employs a light-sensitive
drug to damage an abnormal blood vessel(s). Early detection of
macular degeneration is of paramount importance in preventing
advanced progression of macular degeneration prior to treatment to
inhibit progression of the disease.
Early detection of macular degeneration can be accomplished using a
suitable retinal imaging system. For example, Optical Coherence
Tomography (OCT) is a non-invasive imaging technique relying on low
coherence interferometry that can be used to generate a
cross-sectional image of the macula. The cross-sectional image of
the macula shows if the layers of the macula are distorted and can
be used to monitor whether distortion of the layers of the macula
has increased or decreased relative to an earlier cross-sectional
image to assess the impact of treatment of the macular
degeneration.
BRIEF SUMMARY
The following presents a simplified summary of some embodiments of
the invention in order to provide a basic understanding of the
invention. This summary is not an extensive overview of the
invention. It is not intended to identify key/critical elements of
the invention or to delineate the scope of the invention. Its sole
purpose is to present some embodiments of the invention in a
simplified form as a prelude to the more detailed description that
is presented later.
Ophthalmic imaging systems and related methods employ a viewer
assembly to restrain a user's head in a substantially fixed
position and orientation relative to an optical coherence
tomography (OCT) imaging device and a user specific approach for
controlling the reference arm length in the (OCT) imaging device to
image the user's retina. In many embodiments, the OCT imaging
device includes a reference arm length adjustment module that is
controlled to vary the reference arm length. In many embodiments,
the user engages the user's head with the viewer assembly, thereby
restraining the position of the user's retina relative to the OCT
imaging device. Due to variation between users in the position of a
user's retina relative to the user's facial features (e.g.,
forehead, cheek) engaged with the viewer assembly, as well as
possible variation in the relative position between a user's head
and the viewer assembly, the sample arm length to any particular
user's retina can be within a relatively large range. In many
embodiments, a user specific range of reference arm lengths is used
during imagining of a user's retina. The user specific range of
reference arm lengths is substantially smaller than a reference arm
adjustment range of the reference arm length adjustment module. The
use of the smaller user specific range of reference arm lengths
during imaging of the user's retina substantially reduces the
amount of time expended scanning of the reference arm length to
find the reference arm length at which the OCT image detector
generates the OCT signal for the user's retina, thereby
substantially reducing the total amount of time required to image
the user's retina. Also, by employing a user specific range of
reference arm lengths, the OCT imaging system can be simplified
relative to more complex OCT imaging systems that include a
positioning system to adjust the distance between the OCT imaging
device and the user's retina.
Thus, in one aspect, an ophthalmic imaging system for imaging a
retina includes an optical coherence tomography (OCT) imaging
device, a housing to which the OCT imaging device is attached, a
viewer assembly coupled with the housing, and a control unit. The
OCT imaging device includes a sample arm optical path, an OCT image
detector, a reference arm optical path, and a reference arm length
adjustment module. The reference arm optical path has a reference
arm length. The reference arm length adjustment module is
controllable to vary the reference arm length over a reference arm
length adjustment range. The viewer assembly is configured to
engage a user's head to restrain the user's head relative to the
housing so that the sample arm optical path extends to the user's
retina. The control unit is operatively connected to the OCT image
detector and the reference arm length adjustment module. The
control unit is configured to store a user specific range of
reference arm lengths that covers a smaller range of reference arm
lengths than the reference arm length adjustment range. The control
unit is configured to control the reference arm length adjustment
module to vary the reference arm length to search within the user
specific range of reference arm lengths to identify a reference arm
length for which the OCT image detector produces an OCT signal
corresponding to the user's retina.
Any suitable approach, such as those described herein, can be used
to determine a suitable user specific range of reference path arm
lengths for a particular user for use in the ophthalmic imaging
system. For example, as described herein, the larger reference arm
path length adjustment range of the adjustable reference arm module
can be searched during an initial imaging of the user's retina to
identify a reference path length for which the OCT image detector
38 produces an OCT signal corresponding to the user's retina. The
identified reference path length for the initial imaging of the
user's retina can then be used to formulate a suitable user
specific range of reference path arm lengths for use in subsequent
imaging sessions of the specific user's retina. Alternatively, a
suitable user specific range of reference path arm lengths for any
particular user can be predetermined. For example, the user
specific range of reference path arm lengths can be based on
spatial information about one or more facial features of the user.
In some embodiments, the one or more facial features of the user
upon which the user specific range of reference path arm lengths
can be based include one or more of a forehead of the user, one or
more cheeks of the user, a cornea of an eye of the user including
the retina of the user, and a lateral orbital rim of the user. The
spatial information about one or more facial features of the user
is generated via one or more of: (a) three-dimensional scanning of
the one or more facial features of the user, (b) caliper
measurement of the one or more facial features of the user relative
to an eye of the user that includes the retina of the user, (c) a
cast mask of the one or more facial features of the user, (d) an
axial length of the eye of the user that includes the retina of the
user, (e) ultrasound measurement of the axial length of the eye of
the user that includes the retina of the user, and (f) OCT
measurement of the axial length of the eye of the user that
includes the retina of the user.
In many embodiments, the ophthalmic imaging system lacks a
mechanism to adjust the length of the sample arm optical path. For
example, in many embodiments the ophthalmic imaging system includes
an objective lens assembly and does not include an adjustment
mechanism configured to adjust a distance between the user's retina
and the objective lens assembly.
The lack of an adjust mechanism configured to adjust a distance
between the user's retina and the objective lens assembly results
in a reduced field of view on some user's retinas. To account for
such a reduced field of view, in some embodiments, the ophthalmic
imaging system is configured to image a field of view on the user's
retina equal to or less than 15 degrees for the reference arm
length equal to any length within the reference arm length
adjustment range. In some embodiments, the ophthalmic imaging
system is configured to image a field of view on the user's retina
equal to or less than 10 degrees for the reference arm length equal
to any length within the reference arm length adjustment range.
The OCT imaging device can have a relatively small image depth. For
example, in some embodiments, the OCT imaging device has an image
depth of no more than 3 mm.
The OCT imaging device can have a relatively large sensitivity
roll-off. For example, in some embodiments, the OCT imaging device
has a sensitivity roll off of not better than -3 db at 2 mm.
The user specific range of reference arm lengths can be
substantially smaller than the reference arm length adjustment
range of the reference arm length adjustment module. For example,
in many embodiments, the user specific range of reference arm
lengths is less than half of the reference arm length adjustment
range. In some embodiments, the user specific range of reference
arm lengths is less than one-quarter of the reference arm length
adjustment range.
The control unit can have any suitable configuration. For example,
in many embodiments, the control unit is configured to receive
input of the user specific range of reference arm lengths and store
the user specific range of reference arm lengths in a memory
device. In some embodiments, the control unit is configured to
determine the user specific range of reference arm lengths by
controlling the reference arm length adjustment module during an
imaging of the user's retina to vary the reference arm length to
search within the reference arm length adjustment range to identify
a user specific imaging reference arm length for which the OCT
image detector produces an OCT signal corresponding to the user's
retina. In some embodiments, the control unit determines the user
specific range of reference arm lengths based on the user specific
imaging reference arm length.
The reference arm length adjustment range can encompass a
relatively large range of reference arm lengths. For example, in
many embodiments, the reference arm length adjustment range
encompasses at least a 20 mm range of reference arm lengths. The
reference arm length adjustment range can encompass at least a 30
mm range of reference arm lengths. In some embodiments, the
reference arm length adjustment range encompasses at least a 40 mm
range of reference arm lengths.
The user specific range of reference arm lengths can encompass a
relatively small range of reference arm lengths. For example, in
many embodiments, the user specific range of reference arm lengths
encompasses less than a 10 mm range of reference arm lengths. The
user specific range of reference arm lengths can encompass less
than a 6 mm range of reference arm lengths. In some embodiments,
the user specific range of reference arm lengths encompasses less
than a 4 mm range of reference arm lengths.
In some embodiments, the ophthalmic imaging system includes a
sensor that generates a signal indicative of a position of a
feature of the user's head relative to the housing. In such
embodiments, the control unit can be configured to determine the
user specific range of reference arm lengths based on the signal
indicative of the position of the feature of the user's head
relative to the housing.
In some embodiments, the ophthalmic imaging system includes a
sensor that generates a signal indicative of a position of a
feature of the user's forehead relative to the housing. In such
embodiments, the control unit can be configured to determine the
user specific range of reference arm lengths based on the signal
indicative of the position of the feature of the user's forehead
relative to the housing.
In some embodiments, the ophthalmic imaging system includes a
sensor that generates a signal indicative of a position of a
feature of an eye of the user relative to the housing, wherein the
eye includes the user's retina. In such embodiments, the control
unit can be configured to determine the user specific range of
reference arm lengths based on the signal indicative of a position
of a feature of the eye of the user relative to the housing.
In many embodiments, the viewer assembly includes a compliant
member that accommodates an amount of relative movement between the
user head and the OCT device. For example, in many embodiments, the
viewer assembly includes a compliant member having a thickness that
can change up to 10 mm in response to change in pressure applied to
the viewer assembly by the user's head. In some embodiments, the
viewer assembly includes a compliant member having a thickness that
can change up to 20 mm in response to change in pressure applied to
the viewer assembly by the user's head.
In many embodiments, the ophthalmic imaging system includes a
focusing module that is controlled by the control unit to focus
sample light transmitted over the sample arm optical path onto the
user's retina. A focus setting of the focusing module corresponding
to the user specific imaging reference arm length can be employed
during imaging of the user's retina.
In another aspect, a method of imaging a retina is provided. The
method includes restraining, via a viewer assembly coupled with a
housing and engaged with a user's head, the user's head relative to
the housing so that a sample arm optical path of an optical
coherence tomography (OCT) imaging device attached to the housing
extends to the user's retina. The method includes controlling, by a
control unit, a reference arm length adjustment module of the OCT
imaging device to vary a reference arm length of a reference arm
optical path of the OCT imaging device to search a user specific
range of reference arm lengths to identify a reference arm length
for which the OCT image detector produces an OCT signal
corresponding to the user's retina. The reference arm length
adjustment module is controllable to vary the reference arm length
over a reference arm length adjustment range. The user specific
range of reference arm lengths covers a smaller range of reference
arm lengths than the reference arm length adjustment range. The
method includes imaging, by the OCT imaging device, the user's
retina.
Any suitable approach, such as those described herein, can be used
to determine a suitable user specific range of reference path arm
lengths for a particular user for use in the method of imaging the
retina. For example, as described herein, the larger reference arm
path length adjustment range of the adjustable reference arm module
can be searched during an initial imaging of the user's retina to
identify a reference path length for which the OCT image detector
38 produces an OCT signal corresponding to the user's retina. The
identified reference path length for the initial imaging of the
user's retina can then be used to formulate a suitable user
specific range of reference path arm lengths for use in subsequent
imaging sessions of the specific user's retina. Alternatively, a
suitable user specific range of reference path arm lengths for any
particular user can be predetermined. For example, the user
specific range of reference path arm lengths can be based on
spatial information about one or more facial features of the user.
In some embodiments, the one or more facial features of the user
upon which the user specific range of reference path arm lengths
can be based include one or more of a forehead of the user, one or
more cheeks of the user, a cornea of an eye of the user including
the retina of the user, and a lateral orbital rim of the user. The
spatial information about one or more facial features of the user
is generated via one or more of: (a) three-dimensional scanning of
the one or more facial features of the user, (b) caliper
measurement of the one or more facial features of the user relative
to an eye of the user that includes the retina of the user, (c) a
cast mask of the one or more facial features of the user, (d) an
axial length of the eye of the user that includes the retina of the
user, (e) ultrasound measurement of the axial length of the eye of
the user that includes the retina of the user, and (f) OCT
measurement of the axial length of the eye of the user that
includes the retina of the user.
In many embodiments, the method does not include adjustment of the
length of the sample arm optical path. For example, in many
embodiments, the viewer assembly includes an objective lens
assembly, and the method does not include adjusting a distance
between the user's retina and the objective lens assembly.
The lack of adjusting a distance between the user's retina and the
objective lens assembly results in a reduced field of view on some
user's retinas. To account for such a reduced field of view, in
some embodiments, the imaging of the user's retina is limited to a
field of view on the user's retina equal to or less than 15 degrees
for the reference arm length equal to each of all lengths within
the reference arm length adjustment range. In some embodiments, the
imaging of the user's retina is limited to a field of view on the
user's retina equal to or less than 10 degrees for the reference
arm length equal to each of all lengths within the reference arm
length adjustment range.
In some embodiments of the method, the OCT imaging device has a
relatively small image depth. For example, the OCT imaging device
can have an image depth of no more than 3 mm.
In some embodiments of the method, the OCT imaging device has a
relatively large sensitivity roll-off. For example, the OCT imaging
device can have a sensitivity roll off of not better than -3 db at
2 mm.
In many embodiments of the method, the user specific range of
reference arm lengths is substantially smaller than the reference
arm length adjustment range. For example, the user specific range
of reference arm lengths can be less than half of the reference arm
length adjustment range. In some embodiments of the method, the
user specific range of reference arm lengths is less than
one-quarter of the reference arm length adjustment range.
The method can be practiced using any suitable control unit. For
example, in many embodiments, the method includes (a) receiving, by
the control unit, input of the user specific range of reference arm
lengths, and (b) storing, by the control unit, the user specific
range of reference arm lengths in a tangible memory device. In many
embodiments, the method includes (a) controlling, by the control
unit, the reference arm length adjustment module during an imaging
of the user's retina to vary the reference arm length to search
within the reference arm length adjustment range to identify a user
specific imaging reference arm length for which the OCT image
detector produces an OCT signal corresponding to the user's retina,
(b) determining, by the control unit, the user specific range of
reference arm lengths based on the user specific imaging reference
arm length, (c) storing, by the control unit, the user specific
range of reference arm lengths in a tangible memory device.
The reference arm length adjustment range can encompass a
relatively large range of reference arm lengths. For example, in
many embodiments of the method, the reference arm length adjustment
range encompasses at least a 20 mm range of reference arm lengths.
The reference arm length adjustment range can encompass at least a
30 mm range of reference arm lengths. In some embodiments of the
method, the reference arm length adjustment range encompasses at
least a 40 mm range of reference arm lengths.
The user specific range of reference arm lengths can encompass a
relatively small range of reference arm lengths. For example, in
many embodiments of the method, the user specific range of
reference arm lengths encompasses less than a 10 mm range of
reference arm lengths. The user specific range of reference arm
lengths can encompass less than a 6 mm range of reference arm
lengths. In some embodiments of the method, the user specific range
of reference arm lengths encompasses less than a 4 mm range of
reference arm lengths.
The user specific range of reference arm lengths can be determined
using any suitable approach. For example, in some embodiments, the
method includes (a) receiving, by the control unit, input of the
user specific range of reference arm lengths, and (b) storing, by
the control unit, the user specific range of reference arm lengths
in a tangible memory device. In some embodiments, the method
includes (a) controlling, by the control unit, the reference arm
length adjustment module during an imaging of the user's retina to
vary the reference arm length to search within the reference arm
length adjustment range to identify a user specific imaging
reference arm length for which the OCT image detector produces an
OCT signal corresponding to the user's retina, (b) determining, by
the control unit, the user specific range of reference arm lengths
based on the user specific imaging reference arm length, and (c)
storing, by the control unit, the user specific range of reference
arm lengths in a tangible memory device.
In some embodiments of the method, a sensor is used to measure a
position of the user relative to the housing. For example, in some
embodiments, the method includes (a) generating, by a sensor, a
signal indicative of a position of a feature of the user's head
relative to the housing, and (b) determining, by the control unit,
the user specific range of reference arm lengths based on the
signal indicative of a position of a feature of the user's head
relative to the housing. In some embodiments, the method includes
(a) generating, by a sensor, a signal indicative of a position of a
feature of the user's forehead relative to the housing, and (b)
determining, by the control unit, the user specific range of
reference arm lengths based on the signal indicative of the
position of the feature of the user's forehead relative to the
housing. In some embodiments, the method includes (a) generating,
by a sensor, a signal indicative of a position of a feature an eye
of the user relative to the housing, the eye including the user's
retina, and (b) determining, by the control unit, the user specific
range of reference arm lengths based on the signal indicative of
the position of the feature of the eye of the user relative to the
housing.
In many embodiments of the method, the viewer assembly includes a
compliant member that accommodates an amount of relative movement
between the user and the OCT device. For example, in many
embodiments of the method, the viewer assembly includes a compliant
member having a thickness that can change up to 10 mm in response
to change in pressure applied to the viewer assembly by the user's
head. In some embodiments of the method, the viewer assembly
includes a compliant member having a thickness that can change up
to 20 mm in response to change in pressure applied to the viewer
assembly by the user's head.
In many embodiments of the method, the ophthalmic imaging system
includes a focusing module that is controllable to focus sample
light transmitted over the sample arm optical path onto the retina.
The method can include: (a) storing, by the control unit, a focus
setting of a focusing module of the OCT imaging device
corresponding to the user specific range of reference arm lengths,
and (b) employing the focus setting during imaging of the user's
retina.
In another aspect, an ophthalmic imaging system for imaging a
user's retina includes an optical coherence tomography (OCT)
imaging device, a housing to which the OCT imaging device is
attached, a viewer assembly coupled with the housing, an objective
lens assembly, and a control unit. The OCT imaging device includes
a sample arm optical path, an OCT image detector, a reference arm
optical path having a reference arm length, and a reference arm
length adjustment module controllable to vary the reference arm
length over a reference arm length adjustment range. The viewer
assembly is configured to engage a user's head to restrain the
user's head relative to the housing so that the sample arm optical
path extends to the user's retina. The ophthalmic imaging system
does not include an adjustment mechanism configured to adjust a
distance between the user's retina and the objective lens assembly.
The control unit is operatively connected to the OCT image detector
and the reference arm length adjustment module. The control unit is
configured to control the reference arm length adjustment module to
vary the reference arm length to identify a reference arm length
for which the OCT image detector produces an OCT signal
corresponding to the user's retina.
In many embodiments, the ophthalmic imaging system images a reduced
field of view on the user's retina. For example, in many
embodiments, the ophthalmic imaging system is configured to image a
field of view on the user's retina equal to or less than 15 degrees
for the reference arm length equal to each of all lengths within
the reference arm length adjustment range. In some embodiments, the
ophthalmic imaging system is configured to image a field of view on
the user's retina equal to or less than 10 degrees for the
reference arm length equal to each of all lengths within the
reference arm length adjustment range.
For a fuller understanding of the nature and advantages of the
present invention, reference should be made to the ensuing detailed
description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a user engaged with a viewer assembly of an ophthalmic
imaging system that includes an OCT imaging device, in accordance
with embodiments.
FIG. 2 is a simplified schematic illustration of components and
associated optical paths of the OCT imaging device of the
ophthalmic imaging system of FIG. 1.
FIG. 3 illustrates field of view on the retina when the pupil is
positioned at the focal length of an ophthalmic lens of an
ophthalmic OCT imaging system.
FIG. 4 illustrates a reduced field of view on the retina when the
pupil is positioned away from the focal length of an ophthalmic
lens of an ophthalmic OCT imaging system.
FIG. 5 is a simplified schematic diagram of components of the OCT
imaging device of the ophthalmic imaging system of FIG. 1.
FIG. 6 is a simplified schematic block diagrams of acts of a method
of imaging a retina during an imaging session, in accordance with
embodiments.
FIG. 7 illustrates example search ranges for reference arm path
length for an initial imaging of a particular user's retina and a
subsequent imaging of the particular user's retina, in accordance
with embodiments.
FIG. 8 is a simplified schematic block diagrams of acts for
determining a user specific range of reference arm lengths to
search during a subsequent imaging session for imaging a user's
retina based in part on a sensor measured position of the user, in
accordance with embodiments.
FIG. 9 illustrates example feature based search ranges for
reference arm path length for an initial imaging of a particular
user's retina and a subsequent imaging of the particular user's
retina, in accordance with embodiments.
DETAILED DESCRIPTION
In the following description, various embodiments of the present
invention will be described. For purposes of explanation, specific
configurations and details are set forth in order to provide a
thorough understanding of the embodiments. However, it will also be
apparent to one skilled in the art that the present invention may
be practiced without the specific details. Furthermore, well-known
features may be omitted or simplified in order not to obscure the
embodiment being described.
Referring now to the drawings, in which like reference numerals
represent like parts throughout the several views, FIG. 1 shows a
user 12 looking into a view port 14 of a viewer assembly 16 of an
ophthalmic imaging system 10, in accordance with many embodiments.
The ophthalmic imaging system 10 includes an optical coherence
tomography (OCT) imaging device 18 to which the viewer assembly 16
is coupled. The viewer assembly 16 is configured to be engaged by
the user's head to restrain the user's head relative to the OCT
imaging device 18 to approximately position one eye of the user 12
on an optical axis of the OCT imaging device 18. For example, in
the configuration shown in FIG. 1, the viewer assembly 16 is
configured to approximately position the right eye of the user 12
on the optical axis of the OCT imaging device 18. In the
illustrated embodiment, the viewer assembly 16 can be rotated,
relative to the OCT imaging device 18, 180 degrees around a pivot
axis 20 so as to reconfigure the viewer assembly 16 to
approximately position the left eye of the user 12 on the optical
axis of the OCT imaging device 18. Accordingly, each of the right
and the left eye of the user 12 can be selectively approximately
positioned on the optical axis of the OCT imaging device 18 for
imaging of the respective eye by the OCT imaging device 18. In many
embodiments, final positioning and alignment of the optical axis of
the respective eye of the user 12 with the optical axis of the OCT
imaging device 18 is accomplished by the user 12 adjusting the
position of the user's head relative to the view port 14 in
response to feedback provided to the user 12 by the ophthalmic
imaging device 18.
In many embodiments, the OCT imaging device 18 automatically
adjusts the reference arm path length as described herein during
imaging session in which an OCT image is generated for a user's
retina. The OCT imaging device 18 can have any suitable
configuration that accommodates automatic adjustment of reference
arm path length. For example, FIG. 2 shows a simplified schematic
illustration of components and associated optical paths of an
embodiment of the OCT imaging device 18. The components of the OCT
imaging device 18 illustrated in FIG. 2 include a broadband light
source 22, a dual mirror scanner 24, focusing lenses 26, 28,
dichroic mirrors 30, 32, 34, an adjustable reference arm module 36,
an OCT image detector 38, an eye illuminator 40, an eye camera 42,
and a display device 44. In the illustrated embodiment, the OCT
imaging device 18 is a spectral domain OCT imaging device that
operates in a wavelength range of 800 nm to 900 nm. The eye
illuminator 40 illuminates an eye 46 of the user 12 using a
suitable wavelength of light (e.g., a wavelength of light above 920
nm). The display device 44 can project light between any suitable
wavelength (e.g., from 400 nm to 700 nm). The dichroic mirror 30
transmits the OCT wavelength and the display wavelength range (400
nm to 900 nm) and reflects the illumination wavelength (e.g.,
greater than 920 nm) to the eye camera 40. The dichroic mirror 32
transmits the display wavelength range and reflects the OCT
wavelength.
In operation, the broadband light source 22 generates the OCT
wavelength light. The OCT wavelength light propagates from the
light source 22 to the dichroic mirror 34. A sample arm portion of
the OCT wavelength light passes through the dichroic mirror 34 and
proceeds to propagate along a sample arm optical path 48 to the eye
46. A reference arm portion of the OCT wavelength light is
reflected by the dichroic mirror 34 so as to propagate along a
reference arm optical path that extends into the adjustable
reference arm module 36. The sample arm portion of the OCT
wavelength light is focused on the retina of the eye 46. The OCT
wavelength light focused on the retina is scattered by the retina
so that a backscattered portion of the OCT wavelength light
propagates back along the sample arm optical path 48. The
backscattered portion of the OCT wavelength light passes through
the dichroic mirror 30, is reflected by the dichroic mirror 32 and
the dual scanning mirror 24 back to the dichroic mirror 34, which
reflects the backscattered portion of the OCT wavelength light to
the OCT image detector 38. The adjustable reference arm module 36
includes a reference arm mirror 50 that reflects the reference arm
portion of the OCT wavelength light back to the dichroic mirror 34.
The returning portion of the reference arm portion of the OCT
wavelength light passes through the dichroic mirror 34 to the OCT
image detector 38. In response to the combined incidence of the
returning sample arm OCT light and the returning reference arm OCT
light onto the OCT image detector 38, the OCT image detector 38
generates and outputs an OCT image signal that is processed using
known techniques to build up a three-dimensional OCT image of
layers of the retina. In many embodiments, the OCT image detector
38 detects interference between the returning sample arm light and
the reference arm light only if the time travelled by light in the
reference and sample arms is nearly equal. In many embodiments, the
reference arm mirror 50 is mounted to a motorized mechanism that is
controllable to vary the position of the reference arm mirror 50,
thereby controllably varying the reference arm optical path length.
The ability to vary the reference arm path length enables the OCT
imaging device 18 to be used to generate OCT images of any user's
retina of a desired population of users even though each user's
retina can be at a different distance from the OCT imaging device
18 when the user's head is engaged with the viewer assembly 16 due
to corresponding anatomical variations between user's heads, as
well as variation in the relative position between the user's head
and the viewer assembly 16.
In many embodiments, the eye illuminator 40, the eye camera 42, and
the display device 44 are used to provide feedback to the user 12
by which the user 12 self-aligns the eye 46 with the optical axis
of the OCT imaging device 18. The display device 44 displays a
fixation target that is viewed by the user so as to align the eye
46. The eye camera 42 measures the current position of the eye
relative to the optical axis of the OCT imaging device 18 via
illumination of the eye 46 by the eye illuminator 40. Based on the
measured position of the eye relative to the optical axis of the
OCT imaging device 18, the display device 44 further displays
feedback to the user 12 by which the user adjusts the position of
the user's head relative to the viewer assembly 16 to position the
user's eye 46 within an acceptable distance of the optical axis of
the OCT imaging device 18 for the generation of an OCT image of the
user's retina.
As illustrated in FIG. 3, positioning the pupil at the focal length
of the ophthalmic lens 28 maximizes the area on the retina that can
be imaged by minimizing the amount of sample arm portion of the OCT
wavelength light that is obscured by the iris. In contrast, as
illustrated in FIG. 4, positioning the pupil away from the focal
length of the ophthalmic lens 28 reduces the area on the retina
that can be imaged. Accordingly, in order to image a visual field
of the entire macula (about 20 degrees), existing ophthalmic OCT
systems include a means to adjust the distance between the pupil
and the ophthalmic lens of the OCT system. In some existing
ophthalmic OCT systems, the distance between the entire ophthalmic
OCT system and the user's pupil is adjustable. In some other
existing ophthalmic OCT systems, the position of the ophthalmic
lens relative to the rest of the ophthalmic OCT system is
adjustable so as to adjust the distance between the ophthalmic lens
and the user's pupil. In some other existing ophthalmic OCT
systems, the position of the user's head is moved relative to the
ophthalmic OCT system to adjust the distance between the ophthalmic
lens and the user's pupil.
In existing ophthalmic OCT systems, elimination of the ability to
reposition the pupil relative to the ophthalmic lens would
seriously degrade performance. For example, in existing ophthalmic
OCT systems, elimination of the ability to reposition the pupil
relative to the ophthalmic lens can result in: (a) a large
reduction in the field of view on the retina due to obstruction by
the iris, and/or (b) inability to adjust the reference arm path
length to a length required for imaging the retina where the
existing ophthalmic OCT system lacks sufficient adjustment range
for the reference arm path length.
In contrast to existing ophthalmic OCT systems, in many embodiments
of the ophthalmic OCT systems described herein, the distance
between the user's pupil and the ophthalmic lens is substantially
fixed and the ophthalmic OCT system does not include an adjustment
mechanism configured to adjust the distance between the user's
pupil and the objective lens assembly. To accommodate the lack of
an adjustment mechanism configured to adjust the distance between
the user's pupil and the objective lens assembly, the adjustable
reference arm module 36 is configured to be controllable to vary
the reference arm path length over a reference arm path length
adjustment range that is significantly larger than in current
ophthalmic OCT systems. For existing ophthalmic OCT imaging
systems, adjustment of the reference arm path length only needs to
accommodate variation in the axial length of the eye for different
users. Typical axial length of the eye can vary by +/-3 mm for
(+/-6 Diopter). As a result, adjustment to the reference arm path
length in existing OCT imaging systems does not need to exceed
about 6 mm. In contrast, variation in the location of facial
landmarks relative to the eye are much greater. Facial land marks
can vary in a range of +/-30 mm. Accordingly, in many embodiments,
the reference arm length adjustment range encompasses a relatively
large range of reference arm lengths. For example, in many
embodiments of the method, the reference arm length adjustment
range encompasses at least a 20 mm range of reference arm lengths.
The reference arm length adjustment range can encompass at least a
40 mm range of reference arm lengths. In some embodiments of the
method, the reference arm length adjustment range encompasses at
least a 60 mm range of reference arm lengths.
The larger reference arm path length adjustment range, however, by
itself, would increases the time it takes to search within the
larger reference arm path length adjustment range to identify a
reference arm length for which the OCT image detector 38 produces
an OCT signal corresponding to the user's retina. Increased search
time significantly increases chair time resulting in fixation
losses and increased technician cost. To limit the search time, in
many embodiments described herein, a user specific range of
reference path arm lengths is employed to limit the search to
identify the reference arm length for which the OCT image detector
produces an OCT signal corresponding to the user's retina to a
suitably small range of reference arm lengths for the specific
user.
Any suitable approach, such as those described herein, can be used
to determine a suitable user specific range of reference path arm
lengths for a particular user. For example, as described herein,
the larger reference arm path length adjustment range of the
adjustable reference arm module 36 can be searched during an
initial imaging of the user's retina to identify a reference path
length for which the OCT image detector 38 produces an OCT signal
corresponding to the user's retina. The identified reference path
length for the initial imaging of the user's retina can then be
used to formulate a suitable user specific range of reference path
arm lengths for use in subsequent imaging sessions of the specific
user's retina. Alternatively, a suitable user specific range of
reference path arm lengths for any particular user can be
predetermined based on spatial information about a user's facial
features (e.g., forehead, cheeks, cornea, lateral orbital rim,
and/or any other suitable facial feature) and their relations to
each other. The spatial information about the user's facial
features can be captured/measured in any suitable manner including,
but not limited to, any suitable virtual approach, any suitable
physical approach, and any suitable combination of virtual and
physical approaches. For example, the spatial information about the
user's facial features and/or the suitable user specific range of
reference path arm lengths can be determined based on: (a)
three-dimensional scanning of the user's face, (b) caliper
measurement of the specific land mark on the user's face relative
to the user's eye ball, (c) a cast mask of the user's face, (d)
combinations of (a) through (c) with axial length of the eye (e.g.,
measured via ultrasound, OCT, etc.) combined with measurement of
the distance to the facial land mark to determine the distance of
the facial land mark to the retina, and/or (e) OCT measurement via
the OCT image detector 38.
Moreover, without an adjustment mechanism to adjust the distance
between the user's pupil and the objective lens assembly, a reduced
field of view of the user's retina can result for some users, such
as users with small pupils that are positioned away from the focal
length of the ophthalmic lens 28. To accommodate variability in the
resulting field of view for different users, in some embodiments,
the ophthalmic imaging system 10 images a fixed reduced field of
view for all users. For example, in some embodiments, the
ophthalmic imaging system 10 is configured to image a field of view
on the user's retina equal to or less than 15 degrees for the
reference arm length equal to any length within the reference arm
length adjustment range. In some embodiments, the ophthalmic
imaging system 10 is configured to image a field of view on the
user's retina equal to or less than 10 degrees for the reference
arm length equal to any length within the reference arm length
adjustment range.
In many embodiments, the OCT imaging device 18 is configured to
automatically control components/modules of the OCT imaging device
18 during a imaging session during which an OCT image of a user's
retina is generated. In many embodiments, the OCT imaging device 18
includes a suitable control unit that is operatively connected to
components/modules of the OCT imaging device 18 and configured to
communicate and/or control the components/modules. For example,
FIG. 5 is a simplified schematic diagram illustrating
components/modules of an embodiment of the OCT imaging device 18
that includes a control unit 30 operatively coupled with the
components/modules. The control unit 30 includes a processor 33 and
a data storage device 34. The data storage device 34 stores program
instructions executable by the processor 33 to accomplish the acts
described herein. The data storage device 34 also stores user
specific data as described herein that is used by the processor 33
to customize its control of the operation of the OCT imaging device
18 to the specific user as described herein.
The control unit 30 is operatively connected to the a user
interface 32 to receive input from the user via the user interface
32 and/or to display output to the user via the user interface 32.
Any suitable user interface 32 can be employed including, but not
limited to, one or more push buttons, a display, a touch display,
one or more indicator lights, and/or a speaker. The user interface
32 can be configured to enable a user to input an identification of
the user for a imaging session so that the control unit 30 can
employ scanning parameters stored in the data storage device 34
when controlling the components/modules of the OCT imaging device
18 during a imaging session for the user.
The control unit 30 is operatively connected to the eye illuminator
40, the eye camera 42, and the display device 44. The control unit
30 can turn the eye illuminator 40 on at the start of a imaging
session and off at the end of a imaging session. In many
embodiments, the control unit 30 turns the eye camera 42 on at the
start of the imaging session, receives image data from the eye
camera 42, processes the image data to track the position of the
optical axis of the eye 46 relative to the optical axis of the OCT
imaging device 18, and turns the eye camera 42 off at the end of
the imaging session. In many embodiments, the control unit 30 turns
the display device 44 on at the start of the imaging session,
generates and displays feedback to the user on the display device
44 to enable the user to reposition the user's head relative to the
viewer assembly 16 to sufficiently align the user's eye 46 with the
optical axis of the OCT imaging device 18 for the generation of an
OCT image of the user's retina, and turns the display device 44 of
that the end of the imaging session.
The control unit 30 is operatively connected to the broadband light
source 22, the dual mirror scanner 24, the reference arm length
adjustment module 36, the OCT image detector 38, and a focusing
module 52 to control operation of these components/modules during
an OCT imaging portion of a imaging session. The control unit 22
can turn the broadband light source 22 on to begin transmission of
the OCT wavelength light over the sample and reference arms at the
beginning of the OCT scanning portion of the imaging session, and
can turn the light source 22 off to at the end of the imaging
session. The control unit 30 can control the reference arm length
adjustment module 36 to vary the reference arm length to search for
a user specific reference arm length(s) as described herein for the
respective user for which the OCT image detector 38 generates a
suitable OCT signal for use in generating an OCT image of the
user's retina. The control unit 30 can control the reference arm
length adjustment module 36 to vary the reference arm length to
search within a previously determined user specific range of
reference arm lengths for the respective user to identify a
reference arm length for which the OCT image detector 38 generates
a suitable OCT signal for use in generating an OCT image of the
user's retina. The control unit 30 can also control the reference
arm length adjustment module 36 so as to optimize the OCT signal
generated by the OCT image detector 38 and/or to adjust the
reference arm length in response to movement of the eye 46 relative
to the OCT imaging device 18. In many embodiments, the control unit
30 stores, in the data storage device 34, one or more reference arm
lengths and/or one or more settings of the reference arm length
adjustment module 36 for which the OCT image detector 38 is found
to generate a suitable OCT signal during a imaging session for a
user for use in conjunction with control of the reference arm
length adjustment module 36 during a subsequent imaging session of
the user as described herein. In many embodiments, the control unit
30 stores, in the data storage device 34, a previously determined
user specific range of reference arm lengths, for the respective
user, that is searched during imaging of the user's retina to
identify a reference arm length for which the OCT image detector 38
generates a suitable OCT signal for use in generating an OCT image
of the user's retina. The control unit 30 can control the focusing
module 52 to vary a setting of the focusing module 52 to focus the
sample arm OCT wavelength light onto a target surface of the retina
of the eye 46. The control unit 30 can store, in the data storage
device 34, a suitable setting of the focusing module 52 used during
a imaging session for a user for use as the setting of the focusing
module 52 during a subsequent imaging session of the user as
described herein. In many embodiments, the control unit 30 turns
the OCT image detector 38 on at the start of the OCT scanning
portion of the imaging session, receives an OCT detector output
signal generated by the OCT image detector 38, processes the OCT
detector output signal to generate an OCT image of the retina and
to determine how to control the reference arm length adjustment
module 36 and the focusing module 52 during a imaging session, and
turns the OCT image detector 38 off at the end of the imaging
session. In many embodiments, the control unit 30 controls the
operation of the dual mirror scanner 24 during a imaging session.
During an initial portion of a imaging session, the control unit 30
can control the dual mirror scanner 24 to perform a limited
two-dimensional scan of the sample arm OCT wavelength light
suitable for searching for suitable settings of the reference arm
length adjustment module 36 and/or the focusing module 52 for which
the OCT image detector 38 generates a suitable OCT detector output
signal for the generation of an OCT image of the retina. Once
suitable settings of the reference arm length adjustment module 36
and/or the focusing module 52 are determined by the control unit
30, the control unit 30 can control operation of the dual mirror
scanner 24 to perform a two-dimensional scan of the sample arm OCT
wavelength light suitable for the generation of an OCT image of the
retina.
FIG. 6 is a simplified schematic block diagrams of acts of a method
100 of imaging a retina by an ophthalmic imaging system during an
imaging session, in accordance with embodiments. Any suitable
ophthalmic imaging system, such as the ophthalmic imaging system 10
described herein, can be used to practice the method 100.
In act 102, an identification of a user of the ophthalmic imaging
system is input to the ophthalmic imaging system for use in
controlling an OCT imaging device of the ophthalmic imaging system
during an imaging session. For example, the identification of the
user can be used to retrieve user specific reference arm length
data and/or user specific focus data for use in controlling the OCT
imaging device during the imaging session. The identification of
the user can also be used to store user specific reference arm
length data and/or user specific focus data determined during the
imaging session for use in one or more subsequent imaging sessions
for the identified user.
In act 104, the identification of the user for the imaging session
can be used to determine a suitable reference arm search range for
the imaging session. If no reference arm length data is stored for
the identified user, the reference arm search range for the imaging
session can be set to a default initial search range suitable for a
target population of users that includes the identified user. For
example, FIG. 7 illustrates example search ranges for the reference
arm path length of the OCT imaging device for an initial imaging of
a user's retina and a subsequent imaging of the user's retina. The
search range for the reference arm path length for a subsequent
imaging of a user's retina will typically be smaller than the
search range for the reference arm path length for the initial
imaging of the user's retina because the search range for the
subsequent imaging is determined based on the reference arm path
lengths used to generate an OCT image of the user's retina during
an earlier imaging session(s). During an initial imaging session of
the identified user's retina, the reference arm search range for
the imaging session can be defined between an initial search range
maximum reference arm length 130 and an initial search range
minimum reference arm length 132 suitable for the target population
of users. During a subsequent imaging session of the identified
user's retina, the reference arm search range for the imaging
session can be defined between a user specific maximum reference
arm length 134 and a user specific minimum reference arm length 136
based on reference arm lengths used to image the user's retina
during one or more previous imaging sessions. For example, the user
specific maximum reference arm length 134 can be set by adding a
suitable path length increment to an initial imaging maximum
reference arm length 138 employed to generate an OCT image of the
user's retina during an initial imaging session for the identified
user. Likewise, the user specific minimum reference arm length 136
can be set by subtracting a suitable path length increment to an
initial imaging minimum reference arm length 140 employed to
generate an OCT image of the user's retina during an initial
imaging session for the identified user.
In act 106, the user's head is engaged with a viewer assembly so as
to restrain the position of the user's head relative to the OCT
imaging device during the imaging session. In many embodiments, the
OCT imaging device provides feedback to the user to enable the user
to reposition the user's head to position the user's eye to be
imaged within a suitable distance from the optical axis of the OCT
imaging device and in suitable alignment with the optical axis of
the OCT imaging device for the generation of an OCT image of the
user's retina.
In act 108, with the user's eye suitably restrained relative to the
optical axis of the OCT imaging device, the reference arm length of
the OCT imaging device is varied to search within the reference arm
search range for the imaging session to identify a suitable
reference arm length for use in generating an OCT image of the
user's retina. For example, in the OCT imaging device 18, the
position of the reference arm mirror 50 is controlled by the
control unit 30 to vary the reference arm length within the
reference arm search range for the imaging session. The OCT image
detector output signal is monitored by the control unit 30 to
identify a reference arm length for which the OCT image detector
output signal indicates that the reference arm length matches the
sample arm length close enough for the generation of an OCT image
for the user's retina. To speed the search for a suitable reference
arm length for the imaging session, the extent to which the sample
arm OCT light is scanned in two dimensions during the search for
the suitable reference arm length can be limited as compared to the
two-dimensional scanning used to generate the OCT image of the
retina. When the reference arm search range for the imaging session
is based on the reference arm length(s) used to generate an OCT
image for the user during one or more previous imaging sessions,
the time required to search the resulting user specific reference
arm search range may be substantially reduced relative to the time
required to search the larger reference arm search range for an
initial imaging session for the user.
In act 110, the sample arm OCT wavelength light is focused on the
retina and the reference arm length is adjusted, if necessary, to
optimize the OCT image detector output signal. For example, in the
OCT imaging device 18, the control unit 30 can control the focusing
module 52 to vary the optical power of the focusing module 52 to
vary the focus of the sample arm OCT wavelength light over a target
surface of the retina while monitoring the OCT image detector
output signal to identify a setting for the focusing module 52 that
optimizes the OCT image detector output signal for suitable
locations on the target surface of the retina. Once an optimum
setting for the focusing module 52 is identified, the control unit
30 can control the reference arm length adjustment module 36 to
finely vary the reference arm length while monitoring the OCT image
detector output signal to identify a setting for the reference arm
length adjustment module 36 that optimizes the OCT image detector
output signal for the optimal setting of the focusing module
52.
In act 112, the identified reference path length and the identified
focus setting are used during generation of an OCT image for the
user's retina. In some embodiments, the reference path length is
controlled during the generation of the OCT image to optimize the
OCT image detector output signal throughout the generation of the
OCT image.
In act 114, the reference arm length(s) used to generate the OCT
image during the imaging session is stored in a memory device
(e.g., the data storage device 34 of the control unit 30) so as to
be associated with the identified user for use in determining the
reference arm search range for a subsequent imaging session for the
identified user. If the reference arm path length was varied during
the generation of the OCT image to optimize the OCT image detector
output signal throughout the generation of the OCT image and/or in
response to movement of the eye relative to the OCT imaging device,
a maximum reference arm length and a minimum reference arm length
used during the generation of the OCT image can be stored in memory
device so as to be associated with the identified user for use in
determining the reference arm search range for a subsequent imaging
session for the identified user.
In act 116, a focus setting used during the generation of the OCT
image can be stored in a memory device so as to be associated with
the identified user for use in a subsequent imaging session for the
identified user. For example, in the OCT imaging device 18, the
control unit 30 can store a setting of the focusing module 52 in
the data storage device 34 so as to be associated with the
identified user for use as the setting of the focusing module 52 in
a subsequent imaging session for the identified user.
FIG. 8 is a simplified schematic block diagrams of additional acts
that can be accomplished in the method 100 to determine the
reference arm search range for a subsequent imaging session for the
identified user. In act 118, a sensor generates a signal indicative
of a position of a feature of the user's head relative to the OCT
imaging device. For example, in the ophthalmic imaging system 10,
the sensor can be mounted to the viewer assembly 16 and generate a
signal indicative of a position of a feature of the user's head
relative to the OCT imaging device 18. In act 120, the measured
position of the feature of the user's head relative to the OCT
imaging device is used by a control unit to determine the reference
arm search range for the imaging session. For example, in
embodiments in which the viewer assembly 16 includes a compliant
member that deforms by different amounts in response to different
interface force magnitudes applied to the viewer assembly 16 by the
user's head, the measured position of the feature of the user's
head relative to the OCT imaging device can be used to determine
the reference arm search range for the imaging session so as to
account for the actual gross position of the user's head relative
to the OCT imaging device. By accounting for the actual gross
position of the user's head relative to the OCT imaging device, the
reference arm search range for the imaging session can cover a
smaller range of reference arm lengths as compared to when the
actual gross position of the user's head relative to the OCT
imaging device is unknown. For example, FIG. 9 illustrates an
example non-feature based initial reference arm search range 142
suitable for an initial imaging session for a user for which the
gross position of the user's head relative to the OCT imaging
device is unknown, an example feature based initial reference arm
search range 144 suitable for an initial imaging session for a user
for which the gross position of the user's head has been measured
via a sensor that generates a signal indicative of the position of
a feature of the user's head relative to the OCT imaging device,
and an example feature based user specific reference arm search
range 146 suitable for a subsequent imaging session for a user for
which the gross position of the user's head has been measured via a
sensor that generates a signal indicative of the position of a
feature of the user's head relative to the OCT imaging device. The
non-feature based initial reference arm search range 142 can be
selected suitable for a target population of users and for a
suitable range of expected gross positions between the head of each
of the target population of users and the OCT imaging device. The
feature based initial reference arm search range 144 can be
selected based on a measured gross position of a user's head and
the target population of users. By measuring the actual gross
position of a user's head relative to the OCT imaging device, the
feature based initial reference arm search range 144 covers a
smaller range of reference arm lengths that the non-feature based
initial reference arm search range 142, which accommodates
variation in the possible gross position between the user's head
and the OCT imaging device. The feature based user specific
reference arm search range 146 covers a smaller range of reference
arm lengths that the feature base initial reference arm search
range 144 because the feature based user specific reference arm
search range 146 is based on both the measured gross position of a
specific user's head relative to the OCT imaging device and the
reference arm lengths used during the generation of an OCT image of
the specific user's retina during one or more previous imaging
sessions. In act 122, data defining a relationship between the
reference arm length suitable for the generation of an OCT image of
the user's retina and the position of the feature of the user's
head during the generation of the OCT image of the user' retina is
stored in memory for use during a subsequent imaging of the user's
retina. In act 124, the signal generated by the sensor during a
subsequent imaging session for the user and the data defining the
relationship between the reference arm length suitable for the
generation of an OCT image of the user's retina and the position of
the feature of the user's head during the prior generation of the
OCT image of the user' retina are used to determine the feature
based user specific reference arm search range 146 for the imaging
session.
Other variations are within the spirit of the present invention.
Thus, while the invention is susceptible to various modifications
and alternative constructions, certain illustrated embodiments
thereof are shown in the drawings and have been described above in
detail. It should be understood, however, that there is no
intention to limit the invention to the specific form or forms
disclosed, but on the contrary, the intention is to cover all
modifications, alternative constructions, and equivalents falling
within the spirit and scope of the invention, as defined in the
appended claims.
The use of the terms "a" and "an" and "the" and similar referents
in the context of describing the invention (especially in the
context of the following claims) are to be construed to cover both
the singular and the plural, unless otherwise indicated herein or
clearly contradicted by context. The terms "comprising," "having,"
"including," and "containing" are to be construed as open-ended
terms (i.e., meaning "including, but not limited to,") unless
otherwise noted. The term "connected" is to be construed as partly
or wholly contained within, attached to, or joined together, even
if there is something intervening. Recitation of ranges of values
herein are merely intended to serve as a shorthand method of
referring individually to each separate value falling within the
range, unless otherwise indicated herein, and each separate value
is incorporated into the specification as if it were individually
recited herein. All methods described herein can be performed in
any suitable order unless otherwise indicated herein or otherwise
clearly contradicted by context. The use of any and all examples,
or exemplary language (e.g., "such as") provided herein, is
intended merely to better illuminate embodiments of the invention
and does not pose a limitation on the scope of the invention unless
otherwise claimed. No language in the specification should be
construed as indicating any non-claimed element as essential to the
practice of the invention.
Preferred embodiments of this invention are described herein,
including the best mode known to the inventors for carrying out the
invention. Variations of those preferred embodiments may become
apparent to those of ordinary skill in the art upon reading the
foregoing description. The inventors expect skilled artisans to
employ such variations as appropriate, and the inventors intend for
the invention to be practiced otherwise than as specifically
described herein. Accordingly, this invention includes all
modifications and equivalents of the subject matter recited in the
claims appended hereto as permitted by applicable law. Moreover,
any combination of the above-described elements in all possible
variations thereof is encompassed by the invention unless otherwise
indicated herein or otherwise clearly contradicted by context.
All references, including publications, patent applications, and
patents, cited herein are hereby incorporated by reference to the
same extent as if each reference were individually and specifically
indicated to be incorporated by reference and were set forth in its
entirety herein.
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